diff --git a/src/proxy/tinymitm/ssl.cpp b/src/proxy/tinymitm/ssl.cpp
index 2c1cecf..fc56547 100644
--- a/src/proxy/tinymitm/ssl.cpp
+++ b/src/proxy/tinymitm/ssl.cpp
@@ -105,7 +105,7 @@ WOLFSSL_CTX* CertificateManager::createHostContext(const std::string& host)
     cert->altNamesCrit = 0;
 
     wc_SetSubjectKeyIdFromPublicKey(cert.get(), _sessionKey.get(), nullptr);
-    wc_SetAuthKeyIdFromCert(cert.get(), _caCertDer.data(), _caCertDer.size());
+    wc_SetAuthKeyIdFromCert(cert.get(), _caCertDer.data(), static_cast<int>(_caCertDer.size()));
 
     /*
         cert sign